You can steam syrup sponge in a pyrex bowl. Is it plain cake? So syrup or jam in bottom of bowl, mixture on top, cover top with greaseproof paper, and steam (for a long time, if memory serves!)Chocolate could be steamed with nutella or similar at the bottom?

You can microwave cake, but I think its best eaten straight away.

Oven isn't something silly like off at the mains? or timer button been knocked on???

My suggestion would be to freeze the uncooked batter for another day and make some kind of rocky road/fridge cake if you have the ingredients. open a pack of biscuits or do a mad dash to the supermarket for cake